Need advice about maintenance

[Julian Egelstaff]

Hello,

I have a small rooftop mounted system in Toronto, it's been operational for about four years. (Some of you may have seen my website here: http://www.yourturn.ca/solar/)

Recently, around noon on Friday, it stopped operating.

We have a Xantrex GT2.8 inverter. The display on that simply reads "Inverter Offline."

According to the manual, this means there is either a blown external DC fuse (which we don't have to my knowledge) or there's no DC power coming to the inverter from the array. In low-light conditions, it will say there's insufficient solar energy, and it's not saying that now, so it's not just super cloudy (and it's been three days like this).

My hunch is that something has given out in the wiring between the array and the inverter. I have tried restarting the inverter, and also flipping the switch that shuts off DC power from the array getting to the inverter and then flipping it back on. Neither action had any effect.

I assume that with a volt meter (and I have one of those) I can tell if there is any current on the line from the array? We have a DC cutoff switch in the line prior to the inverter, so if I unscrew the cover on that, I should be able to test that? But I am a total novice at such things, can someone give me the volt-meters-for-dummies story on how to do that? Is it as simple as connecting positive to negative? But it's just Tech 10 guage" cable, so the positive and negative are different strands inside that?

I'd like to have a better idea where the problem is before getting someone out to look at the thing.

Unfortunately, it was installed by Sun Volts which is now defunct. So the other thing I need is recommendations for knowledgable folks in the Toronto area who could service this.

Thanks very much,

--Julian

[Rob Beckers]

Julian, sorry to hear your PV system gave out! It's rare; PV is generally very reliable.

To start with a word of warning: The DC voltage coming into the average grid-tie inverter is usually around 300 Volt. This is deadly. If you think touching the grid AC from a frayed wire is bad, DC is much worse than AC (unlike with AC, the muscles contract and won't release). Just be honest about your DIY skills before taking covers off.

That said, if you take the cover off the wiring compartment of the inverter you should be able to measure if anything is coming in. The DC terminals should have a few hundred Volts on them, especially if the inverter is not working and there's no load on the array. If you inverter has a build-in combiner there may be multiple strings coming in and there would be fuses. If not, then you'll likely have a combiner somewhere outside, with fuses.

If you don't find DC inside the inverter it means something upstream towards the array is wrong and you'd have to work your way backward towards the panels.

-RoB-

[Julian Egelstaff]

Hello,

Thanks for the reply Rob, that's very helpful, and sobering. :-)

There's a combiner box on the roof, that merges the power from the two strings. So from what you're saying, it's possible a fuse in there has blown? That makes some sense. If that is the case, then I ought to find zero power on the DC terminals in the inverter, I assume, if I've understood what you wrote?

My house is three stories so I'm not climbing up on the roof myself! How necessary is it to have a solar person check this out, versus a proper electrician? If it is just a fuse, any real electrician could deal with it on the roof?

--Julian

[Rob Beckers]

Julian, normally each string is fused when it comes into the combiner box, then combined, and from there it goes to the inverter. Sometimes the inverter is fused too. What that means is that unless the fuses of all the strings blew there would still be some voltage going into the inverter (and power coming out). An unlikely event.

Who's best would depend; A solar person that knows what he/she is doing would know better how to track this down vs. an electrician (most electricians know little about PV). Then again, an electrician familiar with PV would of course be able to do the job too.

-RoB-

[Julian Egelstaff]

Hello,

I should provide an update...I called Solsmart in Toronto. They sent a technician out, who quickly figured out that the problem was in a switch box in the basement that sits between the roof and the inverter. There were a couple fuses in that switch, and one was blown.

The fuses were AC fuses, which the technician said were somewhat common in such situations back in 2009 when the system was installed, because there was less DC equipment available in Ontario readily. So a high voltage AC fuse was used instead. And obviously worked for a while.

Solsmart procured some DC fuses for the switch and came over to install them, and the system has been working fine ever since.

--Julian